This invention relates to bearing structures and more specifically to an improved bearing assembly for venting a wheel bearing used on boat trailers, conveyors and the like.
Prior art sealed bearings are packed in grease without adaquate pressure relief. Excessive pressure build-up in these bearings during outside temperature change as well as heat produced therein by friction during normal trailer operation causes expansion of the packing grease and the consequent compression of air trapped in the bearing chamber. Such excessive pressures are undesirable in that they force grease through the sealing surfaces of the bearings relieving pressure therein and they contribute to early failure of the bearing structure.
The towing of the boat trailer to the boat launching site also causes bearing and grease friction which generates heat within the wheel hub. This heat causes pressure to build up within the hub which in turn causes air and grease within the hub to escape through the rotating seal. Then, at the boat launching site, when the boat trailer is backed into the water to launch the boat, the submerged hub is suddenly cooled by the water. This cooling contracts the air inside the hub and creates a partial vacuum therein which causes water and silt to seep into the hub. The resulting rust and erosion inevitably causes bearing damage.